The present invention relates to nanoparticles. More specifically, the present invention relates to the deposition of charge and/or nanoparticles.
There is an ongoing trend to miniaturize components and devices. Smaller components and devices allow more complex functions to be performed in a smaller volume and, in some configurations, can increase speed and reduce power consumption of a device. Small components have also found use in the biological and medical sciences. Today's forefront of miniaturization is generally referred to as “nanotechnology”. One technique used in nanotechnology is based upon the use of organic and inorganic “nanoparticles”.
Nanoparticles are considered the building blocks of many future nanotechnological devices. Nanoparticles are typically created in the gas or liquid phase. Most well known techniques include metal evaporation, laser ablation, solution vaporization, wire explosion, pyrolysis, colloidal and electrochemical synthesis, and generation from plasmas. Nanoparticles are of current interest for electronic and optoelectronic device applications, Silicon nanoparticles generated by silane pyrolysis or electrochemical reaction of hydrogen-fluoride with hydrogen-peroxide are used for non-volatile memories, lasers; and biological markers. Evaporated gold, indium, and ion sputtered aluminum nanoparticles are used for single electron transistors; and electron beam evaporated gold and silver particles are used for plasmonic waveguides. However, devices do not hold the only interest in nanoparticle generation. Nanoparticles also provide the foundation for the development of new materials and act as catalysts in nanowire synthesis.
The use of nanoparticles as building blocks, regardless of the application, requires new assembling strategies. Most actively studied approaches include: i) single particle manipulation, ii) random particle deposition, and iii) parallel particle assembly-based on self-assembly. Single particle manipulation and random particle deposition are useful to fabricate and explore new device architectures. However, inherent disadvantages such as the lag in yield and speed, will have to be overcome in the future to enable the manufacturing of nanotechnological devices. Fabrication strategies that rely on mechanisms of self-assembly can overcome these difficulties. Self-assembly techniques have begun to be used to assemble nanoparticles onto substrates. Current areas of investigation use geometrical templates, copolymer scaffolds, protein Recognition, DNA hybridization, hydrophobicity/hydrophilicity, magnetic interactions, and electrostatic interactions.
Stimulated by the success of atomic force based charge patterning, high resolution patterns have been used as templates for self assembly and as nucleation sites for molecules and small particles. Several serial charge-patterning processes have been explored to enable the positioning of nanoparticles. Scanning probe based techniques, for example, have been developed to pattern charge in silicon dioxide and Teflon like thin films. Serial techniques, however, remain slow—the fastest scanning probe-based system needs 1.5 days to pattern an area of 1 cm2. This experimental bottleneck has led to the development of electric nanocontact printing to pattern charge in parallel. Electric nanocontact printing generates a charge pattern based on the same physical principles used in scanning probes but forms multiple electric contacts of different size and shape to transfer charge in a single step. With this method, patterning of charge with 100 nm scale resolution and transfer of 50 nm to 20 μm sized particles including iron oxide, graphite carbon, iron beads, and toner can be achieved. As a result several research groups have began investigating charge based printing. Krinke et al. assembled indium particles from the gas phase onto charged areas created by contact charging using a scanning stainless steel needle (T. J. Krinke et al., Applied Physics Letters, 2001, 78, 3708); Mesquida and Stemmer demonstrated the assembly of silica beads and gold colloids from the liquid phase onto charged areas created by contact charging using a scanning probe (P. Mesquida et al., Microelectronic Engineering, 2002, 61–62, 671; and P. Mesquida et al., Surface and Interface Analysis, 2002, 33, 159); and Fudouzi et al. demonstrated the assembly of SiO2 and TiO2 particles from both the liquid and gas phase onto charged areas created by focused ion and electron beams (H. Fudouzi et al., Langmuir, 2002, 18, 7648; and H. Fudouzi et al., Materials Research Society Symposium Proceedings, 2001, 636, D9.8/1).
However, there is an ongoing need for improved techniques and apparatus for the deposition and formation of nanoparticles and devices which use nanoparticles. One example technique is described in U.S. patent application Ser. No. 10/316,997, entitled ELECTRET MICROCONTACT PRINTING METHOD AND APPARATUS.